The present invention relates generally to an improved vacuum cleaner and, in particular, to a compact vacuum cleaner in which the discharge of the air to the outside of the cleaner is diminished as much as possible, so that dust may be collected by the air which is recirculated in the cleaner.
In the conventional vacuum cleaner, the air suspending the collected dust is made to pass through a filter and into a dust collecting sack before it is discharged to the outside of the cleaner. Consequently, most of the collected dust is arrested by the filter and the dust collecting sack. However, the filter and the dust collecting sack cannot arrest invisibly fine particles of dust. As a result, these fine particles are carried away by the air and discharged out of the cleaner together with the air. Consequently, the user is forced to inhale the fine dust into the body during the use of the cleaner. This is quite undesirable from the stand point of sanitation.
This problem is serious especially when the fine dust particles discharged together with the air contains noxious components. In such a case, the user who is engaged in the cleaning inhales the noxious component during the repeated use of the cleaner over a long term, so that the user, especially the respiratory organs of the user may be seriously damaged.
For instance, there is a good deal of chalk dust around the blackboards used in schools. Usually, wipers made of cloth are used to erase the letters and patterns marked on the blackboard by the chalk. As is well known, the chalk dust is scattered when these wipers are used. Consequently, the user of the wiper is forced to inhale the chalk dust, and his respiratory organs are seriously damaged during the repeated use of the wiper. This problem cannot be overcome even by the use of a vacuum cleaner in place of the wiper made of cloth, because the conventional vacuum cleaner cannot prevent the noxious fine chalk dust particles from being released into the ambient air, as stated before.